They are likely the first standing stones you will encounter, since they are on the path taken while being escorted by Ralof or Hadvar to Riverwood. The stones are The Mage Stone, The Thief Stone, and The Warrior Stone. If selected, they allow you to specialize in magic, stealth or combat skills respectively, by gaining 20% more experience in those skills. Archery is considered a stealth skill in this context.

The Mage Stone: Those under the sign of The Mage will learn all magic skills 20% faster.

The Thief Stone: Those under the sign of The Thief will learn all stealth skills 20% faster.

The Warrior Stone: Those under the sign of The Warrior will learn all combat skills 20% faster.